Sender control system



Feb. 24, Q M|| ER SENDER CONTROL SYSTEM Filed Sept. 1l, 1940 4 Sheets-Sheet 1 /A/I/E/VTOR ce. M/LLER 6. m

A TTORNE-V Feb. 24, 1942. c. G. MILLER 2,274,083

SENDER CONTROL SYSTEM Ill-Il' A TTORNE Y Feb24', 1942. c. G. MILLl-:

SENDER CONTROL SYSTEM Filed Sept. 11, 1940 4 SheebS-Shee'I 3 /NI/ENTOR y 4 6.a M/LL ER 6.36. m'pa ATTORNEY Feb. 24, 1942. C, G MILLER SENDER CONTROL SYSTEM Filed Sept. l1, 1940 4 Sheets-Sheet 4 /A/l/E/v TOR C. G. M/LL E R A TToR/VEV w22 4 vwo. b funnI M @u gok Patented Feb. 24, 1942 g STAT PATENT v0 F F I CE `CONTROL SYSTEM Charles GL Miller,.Montclair, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York; N; YL', a'corporation of New York Application. September 11, 1940i Serial No. 356,286

1'7 Claims.

This invention relates to telephone systems and has for its object the reduction of delay'sfdue to :peak traiiic loads.`

In designing telephone/cuites' the amount of control: equipment tov befprovided is based on handling' ord-inarilyheavy traffic loads with a given srnalldelay, andthere" is practically no delay during the 'greater-'parto-the time; 'Ori rare occasions someI event will causef'an' unusual risein the numberoi calls originated at'a :pare ticular cnice, resulting in la shortage of control equipment `which may persist 'f forv an appreciable lengtlfrofl time: Slow dialing by-unfami'liar sub-Y soribers whenvan oiice is rst introduced into service'may valso resul-t in overloaded control equipment andundue-A delays. 'Heretofo're there has been no' positive rneansiorftelling the subscriber `of delay in cases-'of at shortage in control equipment.

Ini accordance the' present invention', means is providedI forgiving special treatment to a proportion of the: incoming Y callswhen the originating` control devices or senders arev ap-` proaching an all busycondition.' This treat-` mentmay consist of giving anequipment-busy signal or. it mayiliein reroutingr thecall-toan Aloperator. l

Means' is provided undervthe' control of-a `reflay operatedv when- .a 4predetemnined number of groups of` originatingfsenders are busy4 to ree' move a. certain number of senders Vfronrregular service and arr-ange. them to direct the calling line by which they. are seized. to ant overflow trunk immediately, Since thistakes from Ione to two seconds as against an average of from 4,iiiteen to sixteen seconds for. completinga call, the rsenders removed from. regular servicecan dispose `of eight to ten., calls While the senders in regular service dispose ofonecall.

Moreover, the allocation, WhenV an.v overload becomes imminent; of particular. senders tothe rapid4` disposition of calls. entering; them-mitif` gates. very materially the condition arising from subscribersjdialing before senders are connected to their lines. This premature dialing. takes place when undue delay occurs, and the senders, as' they connect to the lines, receive either partialfsets of pulsesor no pulses at all, are' thereby held out of other service for unusual pe`` ri'ods of timel awaitingpulses whichV fail to are rive, andan overloadedfsender group situation `is` pyramided. l

Peak traiiic conditions of afdegree rofqseverity which this invention cares for persist? but for shortv periods oftim'e when. the' inventiony use. Calls disposed Vof 'temporarily by the senders made special when an overload impends are not connected' to the subscribers called, but are given an equipment busy signal, and l consequently are in large measure vrepeated later. However, the probability of these calls then being placed at a time of sender group overload, or o'i' impending overload, is very much less than Whenthey first Were` placed because of the short duration 'of the traiiic peaks.

When the invention is used at times of impending overload to'route'calls entering the spe'- cially arranged senders to A operators, then the rerouted calls' 'are completed b y giving they Wanted number orallyV to the A operators. These operatorsuseA operatorsV senders which are not subject tof subscriberV Vdelays in dialing and also are not likely to be carrying peak traffic at the same time as the other senders.

f Itis by one or the other of the foregoing methods, then, that the invent-ion functions in taking care of traic peaks Without unduly increased delay in the connectionof control equipment.

The senders removed from regular servicearey at the same time arranged'tc prevent the transmission of dial tone and to make'dialing ineiiective if the subscriber should start to dia-14 without waiting for dial tone, anda vmarker is seized and a, special code transmitted thereto immedi-v ately after the sender is taken for use.'4 In such senders also, the party` linetest check is canceled and calls fromv coinlines; may or may not be completed in the usual manner. L

In the marker the special code causesthe op eration of a, route relay which may be cross-'connected to direct the connection from the line to an overflow trunk which transmits anall equipment `busy tone to` the calling line, or the route relay may direct the line to an A operators position', who can thencomplete the call.

These and other fea-tures :of the inventionwill be more" clearly understood from a consideration o f the 4following.description lin connection with the drawings, in which:

Fig. 1 shows asubscribens line and parts of the'line link and sender link, a district junctor and district and office switches;

Fig. 2 shows the traffic register circuit;

Figs. 3 and 4 show portions Otan originating sender; and

Fig. 5 shows the arrangement of Figs.A 1 to 4'.

The: drawings show the modifications necessary vin a. standard originating sender of` the cross-bar telephone system in order to embody `therein' the'features of the invention. Such a standard sender is shown and described in detail in Patent 2,235,803, granted on March 18, 1941 to W. W. Carpenter, and for convenience in consulting that disclosure, the same reference characters have been used wherever possible.

As set forth in the above-mentioned Carpenter patent, when a sender has been seized and is ready to handle a call, relay 3000 operates, in turn operating one of the individual sender busy relays 24I2?.4 I4 in the sender link circuit. lThe senders are arranged in groups of ten and as each sender is seized the corresponding busy relay 24I2, 24I4, etc., is operated. When all of the senders of a group are busy, a group busy relay 2405 is operated over a chain circuit extending over the front contacts of the individual busy relays. Relay 2405 in operating connects ground through resistance 2430 to battery through the left winding of relay 24I5. As other groups of senders become busy, similar group busy relays connect similar resistances to the left winding of relay 24I5 in parallel with resistance 2430, thereby increasing the current flow through that winding. Relay 24|?) is a polarized relay of the permanent magnet type and its two windings are differentially connected. The right winding of the relay is cross-connected through terminal blocks 24|6 and 24I1 to some one of the associated resistances. These resistances are graded in value so that the current through the right winding may be set at a desired value by connecting with the proper resistance. The current flow through the right Winding tends to hold the relay Contact open while that through the left winding tends to close it. Due to the diierential arrangement of the windings the relay will remain non-operated until its left winding receives sufficient operating current to prevail over the right winding and the polarizing effect of the relay structure. lWhen the predetermined number of sender groups for example six, have become busy, relay 24I5 operates, in turn operating relay 200. With relay 200 operated, interrupter 20| is connected to relay 202 and the relay follows the interrupter, operating meter 203 and relay 204. Relay 202 locks to a back contact of meter 203 to insure the'operation ofrneter 203, which scores once for every interrupter operation, thereby recording the duration of the groups busy condition. Relay 204 locks under the control of key 205, lights lamp 206 and sounds an alarm.

Responding to the alarm, the maintenance man may attempt to silence the alarm by opening key 205, and note whether the condition clears itself or persists. If it persists, as indicated by the intermittent operation of the alarm, he may close key 201, thereby operating relays 203 and 209 and, in turn, relay 2I0'. Relays 208 and 209 are slow to release and are used to prevent release of relay 2I0 if the number of senders busy should drop during a short' period of lighter traic to a point where relay 24|5 releases.

With relay 2|0Voperated, battery is connected to conductor 2II leading to the sender shown and'to four similar conductors leading to four other senders which are not shown. This battery connection serves to place the sender in condition for giving special handling to calls reaching it. According to the arrangement being described there is one relay 2|0 for fifty senders and each relay 2I0 marks ve senders or ten per cent for special service, which is one sender for each sender frame.

A brief outline of the normal operation of the parts of the system shown is now given as a basis for describing the invention further:

When a call is originated, for example by the subscriber at substation |000, line relay |006 is operated, in turn operating horizontal group relay |009 through a preference arrangement, not shown. With relay |009 operated, relay |008 is operated to connect ground from the inner contact of line relay |006 to conductor |046 and thence to the relay IBI I which indicates the position of line |000 in its group of ten lines. Relay I8I2 and relay II3 are connected with other line relays of the same group. As set forth in the above-identiiied Carpenter patent, the position of the line in the group is used to identify the class of service to which the line belongs, and therefore the operation of one of the relays |0| l, I8I2, II3, etc., may be used to transmit this information to the sender. In the present disclosure relay ISII is connected to individual lines, relay I8I2 to two-party lines and relay |I3 to coin lines.

After a line has been isolated to be served, the line link is connected with a sender link serving a group of district junctors which includes an idle district and for which there are idle sender link switches leading to idle groups of senders. This connection is established by means of relay |32 I. The sender link then picks an idle district junctor, an idle sender and a set of switches to connect them and makes a temporary connection with the sender, during which relay 2900 is operated and the class of service registration is set up on relays 2905, 300, 2904, etc., these relays being connected to contacts of relays I8I I, |I3 and I8I2, respectively. Relays 2905 and 300 operate relay 3002, which is operated from relay 3001 under the control of relay 2904 on calls from two-party lines. While relay 2900 is operated, a circuit is completed for relay 3000 which locks under the control of relays not shown. Relay 3000 operates the sender busy relay 24I2. When the primary and secondary sender selectors have been operated, relay 2900 is released and the dialing circuit is closed from ground through the left winding of dial tone coil 3004, outer left front contact of relay 3002, inner left front contact of relay 3000, conductors 3020, 245|, 2048, 2549, 2559, I08I which connect the sender and line switches, through substation |000, through the line and sender switches over conductors |082, 2533, 2550, 2041, 2450' and 30I9, middle left contact of relay 3000, inner left front contact of relay 3002, middle winding of relay 3602 to battery.

The subscriber, hearing the dial tone, operates his dial, intermittently releasing relay 3602, which closes a circuit from ground on conductor 3024 over the back contact of relay 3602 and a back contact 4of relay 400 to control the pulsing relays.

When the oflice designation has been recorded,

marker 40| is connected over marker connector 402 to the cross-bar register 403 from which it receives the oiice designation and from it controls the extension of the calling line through the district junctor and over the district and oflice switches to the terminating office, after which the marker is released. The sender either controls the equipment at the terminating office or transmits the numerical designation to that oice before returning to normal.

Assume now that a peak overload has occurred, key 201 has been operated and battery has been connected to conductor 2|I. With relay 3000 normal, that is, as soon as the sender has finished with the call being handled, a circuit is completed fromk battery on' conductor 2II, upper winding of relay 400, outerright .normal contacts of 'relay 3000 to ground. When relay 300'0foper-- ates following the seizure of the sender, a locking circuit is closed for relay 400 4from battery over the lower 'winding andinner lower front contact of relay 400, left back `contact of relay 30|, to ground at thel outer right alternate contacts of relay 3000; Relay 400 is therefore held oper; ated until the sender completes its function with a calling line, even though battery maybe removed frorn conductor 2II intheime'antime;

When the line has been connected't'o the sender andfmrelay 3602 operated, ground is connected" to the 'second lower contact of -relay 400'wh-ich operates .relay 38I2 to..summon a marker. At its four lower contacts relay 400v connects direct `ground to conductors 3255 and 3256 and connects checking conductor 3048 toconducto'rs-3251 and 3250-, thereby establishing.' a specialcode in the marker which will be translated to cause' the marker to Vconnect the line to an overflow trunk. As mentioned above, whereV desirable the mar-ker may cause the line to be connected to an A operators position by varying the' cross-connections on the route relay operated in response to the' special code.

In order to discourage dialing by the subscriber, which would serve no purpose and would be likely to delayhis receipt of busy tone'k ory the response of the A operator, relay' 4005in operating opens theprimarycircuit ofth'e'dial tone coil 3004. In addition, it opens the connectionlbe l tween the pulsing' contact of relay 3602 and -the pulsing relays so that, if the subscriber' operates his dial without waiting for the dial tone, no registration will'be made which might interfere with the operation of the marker.

When a call is received from a two-party line, class of service relay2004 is operated. In this case, the sender tests the line before dialing starts to determine which party is calling. Normally the sender retests'the line after dialing is completed, and compares the twov tests to -detect attempts to charge the call to the wrongparty. With relay 2004 operated, relay 3002-is not operated immediately thereafter, as in thecaseof relay 2905. When relay 3000 operates, the tip and ring conductors are connected over the left front contacts of relay 3000, the left back con` tacts of relay 3002 inv parallel and thence 'over the inner right front contact of relay 2904 to'the winding of relay 3008 and battery. If' theu tip party is calling, the line is grounded and relay 3008 operates. If the ring' party isk calling, no ground is present and relay 3008 does not opcrate., If relay 30084 operates, a circuit is closed from ground over the outer and inner right vfront contacts of relay 3000, front contact of' relay 3008, back contact of relay 3100, windingof relay 30H and battery.

WhenA relay 2904 first operated, it'connected ground over its outerV right contact to the -lower Winding of relay 3001 through resistance 3005 and condenser 3006, and until relay 3000 operates, this ground also extends over thek inner right back contact of relay 3000' to the lower winding cf relay 30Min shunt of condenser 35006 and resistance 3005, energizing that relay in a direc-2 tion to hold'its contact open. When relay 3000 operates, this ground is transferred to `the v'upper winding of relay 3001 to'operate it, butdue-to the charging of cond'enser3006'- the operation is delayedto give time for the test above described; When' relay `3001 closes its contact, relay 3002isoperatedand locks under the control of relay 31091`and the sender is ready to receive dial. pulses; Thistest is not affected by the operation Vofr'elay 400in the sendersselected for special. service. With relay 3002 operated and 1e1ay3700fnormal the energizing circuit for the lower winding of relay 3001 is restored, aswell as the shunty around condenser 3006, thereby causing relay 3`001'to open its contact.

In normal operation, relay 3109 operates following the. completion of dialing and releases relayr 3002; With relay 3002k released, thetip and: ring conductors are again connected to relay 3000,' which, ifoperated, operates relay 30I0 over the'left front contact of relay 3100. Relay 3109 alsoiopehsA the.circuits for the lower winding of timing'relay 3001 permitting that relay toreoperate, in'V turn reoperating relay 3002. When the sender-is ready to release, conductor 3025 is groundedV and` if relays 30I I and 36H0 are both operatedor both non-operated a circuit is closed from ground onconductor 3025, third right front Contact of relay 3002, over both front or both back contacts.: of relays 30I0 and 30H to the winding of relay 3IOI and battery. The operation of relay 3 IOI starts the chain of events which result in therelease of the sender. If this relay failsl tot operate, the sender times out and the connection cannot be completed.

l Since none of the calls given special handling is completed by this sender, this check of the party test is canceled by the operation of relay 400 which closes av circuit for relay 3IOI 'over the third contact of lrelay 400't0 the third right contact of relay 30Min` shunt of the contacts of relays 30'l0and 30| I.

ForV those` oiiices where the specially handled calls are1 directed to an A operators position which is :not equipped for coin collection or re fund',v the' special handling of calls from coin box linesiscanceled by'the class of service relay 300. With relay 300 operated,r in turn operating` relay the locking circuit of relay 400 is opened and, as soon as relay 3000 operates, opening the operating circuit of relay 400, relay 400 releases, restoring the sender to normal service. Where specially handled calls are routed to an overflow trunk the back contacts of relay 30| may be permanently connected together, and calls from coin lines handled the same as other calls.

What is claimed is:

1. In a telephonesystem, telephone lines, automatic switching equipment, register senders, means in said register senders under the control of a subscriber on onefof said lines for operating said switching equipment to connect said` line with a second liney for conversation', and means effective when the senders-busy condition is such as to indicate the likelihood of an imminent trafc peak for giving special routing to a proportion of the originating calls.

2; Ina telephone system, telephone lines, autoy matic switching equipment, control equipment,

means in said control equip-ment under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, and

r j meansy eiTective whena predetermined busy condition of said control equipment occurs forrnodie fying certain of said control equipment to give calling'subscribers an over'ow signal.

3. In a telephone system, telephone lines, aus

f tomatic switching equipment, control equipments,

means in said control equipments under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, and means effective when a predetermined busy condition of said control equipments occurs for modifying a predetermined fraction of said control equipments to give an overflow signal to a proportion of the originating calls.

4. In a telephone system, telephone lines, automatic switching equipment, control equipment, means in said control equipment under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, means effective when a predetermined busy condition of said control equipment occurs for giving special routing to a proportion of the originating calls, and means to render said special routing means effective during a predetermined period following the termination of said busy condition.

5. In a telephone system, telephone lines, automatic switching equipment, control equipment, means in said control equipment under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, means eiective when a predetermined busy condition of said control equipment occurs for giving a special routing to a proportion,n of the originating calls, A

and means to render said special routing means effective during short predetermined periods of interruption of said busy condition.

6. In a telephone system, telephone lines, automatic switching equipment, control equipment, means in said control equipment under the control of a subscriber on one oi said lines for operating said switching equipment to connect said line with a second line for conversation, and means effective when a predetermined busy condition of said control equipment occurs for rendering certain of said control equipment unresponsive to subscriber control and for arranging said certain control equipment to immediately connect a calling line with an overflow signal means.

7. In a telephone system, telephone lines,

, automatic switching equipment, control equipment, means in said control equipment under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, and means eiective when a predetermined busy condition of said control equipment occurs for rendering certain of said control equipment unresponsive to subscriber control and for arranging said certain control equipment `to immediately connect a calling line with an operators position.

8. In a telephone system, telephone lines, automatic switching equipment, control equipment, means in said control equipment under the control of a subscriber on one of said lines for operating said switching equipment to connect said line with a second line for conversation, and means effective when a predetermined busy condition of said control equipment occurs for rendering certain of said control equipment unresponsive to subscriber control and for arranging said certain control equipment to immediately connect a calling line with a special trunk.

9. In a telephone system, telephone lines, automatic switching equipment, register senders. means in said senders for registering the designations of wanted telephone lines, decoder markers operated in accordance with registered designations for controlling said switching equipment to extend a calling line to the ofce in which the wanted line is located, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said modifying means for preventingr the registration of a line designation.

10. In a telephone system, telephone lines, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, decoder markers operated in accordance with registered designations for controlling said switching equipment to extend a calling line to the ofce in which the wanted line is located, means effective when the senders-busy condition is such as to indicate the likelihood of an imminent traic peak for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said modifying means for preventing the registration of a line designation.

ll. In a telephone system, telephone lines, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, decoder markers operated in accordance with registered designations for controlling said switching equipment to extend a calling line to the office in which the wanted line is located, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said modifying means for transmitting a special designation to one of said decoder markers to cause said decoder marker to extend the calling line to an overflow signal means.

12. In a telephone system, telephone lines,

automatic switching equipment, register senders,

means in said senders for registering the designations of wanted telephone lines, decoder markers operated in accordance with registered designations for controlling said switching equipment to extend a calling line to the oiice in which the wanted line is located, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said modifying means for preventing the registration of a line designation and for transmitting a special designation to one of said decoder markers to cause said decoder marker to extend the calling line to an overflow signal means.

13. In a telephone system, telephone lines having a plurality of substations thereon, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, means for testing a calling line and identifying the calling substation before said designation is recorded, means for retesting said line after said designation is recorded, means for preventing the release of said sender if said test and retest do not identify the same substation, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special routing to originated calls directed thereto, and means under the control of said modifying means for canceling saidA retest and for releasing said sender.

14. In a telephone system, telephone lines having a plurality of substations thereon, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, means for testing a calling line and identifying the calling substation before said designation is recorded, means for retesting said line after said designation is recorded, means for preventing the release of said sender if said test and retest do not identify the same substation, decoder markers operated in accordance with registered designations for controlling said switching equipment to extend a calling line to the o'ce in which the wanted line is located, means voperated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said modifying means for preventing the registration of a line designation, for transmitting a special designation to one of said decoder markers to cause said decoder marker to extend the callingline to an overflow signal means, and for canceling said retest and releasing said sender.

15. In a telephone system, telephone lines of a plurality of classes, automatic switching equipment, register senders, means in said senders for registering the designation of wanted telephone lines, means for recording the class of a calling line, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said class recording means for rendering said modifying means ineffective.

16. In a telephone system, telephone lines of a plurality of classes, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, means for recording the class of a calling line, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said class recording means if the calling line is of a particular class for rendering said modifying means ineffective.

17. In a telephone system, telephone lines of a plurality of classes, automatic switching equipment, register senders, means in said senders for registering the designations of wanted telephone lines, means for recording the class of a calling line, means operated when a predetermined busy condition of said control equipment occurs for modifying a percentage of said senders to give special handling to originated calls directed thereto, and means under the control of said class recording means if the calling line is one equipped with a coin box for rendering said modifying means ineffective.

CHARLES G. MILLER. 

